- A
The firewall is using a forward trust certificate that is expired.
Why wrong: An expired certificate would cause errors, but likely the certificate is self-signed and not trusted.
- B
The decryption policy is not applied to the correct security rule.
Why wrong: Decryption is applied via decryption policy, not security rules; order might matter but not the cause of certificate error.
- C
The firewall's decryption root CA certificate has not been installed in the client's trusted root certificate store.
Correct. Clients must trust the firewall's issuing CA to avoid certificate warnings.
- D
The decryption policy is set to 'no-decrypt' for the traffic.
Why wrong: If set to no-decrypt, traffic would pass through without decryption, so no certificate error from the firewall.
PCNSE Core Concepts and Architecture Practice Question
This PCNSE practice question tests your understanding of core concepts and architecture. This is a configuration task: choose the command set that satisfies every stated requirement. Small differences — like 'secret' vs 'password' or 'transport input ssh' vs 'all' — change whether the answer is correct. After answering, compare your reasoning against the explanation and wrong-answer breakdown below. Once you have made your selection, read the full explanation to reinforce the concept and understand why each distractor is designed to mislead on exam day.
A company configures its Palo Alto Networks firewall to decrypt outbound SSL traffic using a forward proxy. After applying the decryption policy, users report that their browsers display certificate errors when accessing HTTPS websites. The firewall's decryption certificate is self-signed. What is the most likely cause?
Clue words in this question
Noticing these words before you look at the options changes how you read each choice.
Clue:
"most likely"Why it matters: Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
Answer choices
Why each option matters
Answer the question above first, then reveal the full breakdown to understand why each option is right or wrong.
Correct answer & explanation
The firewall's decryption root CA certificate has not been installed in the client's trusted root certificate store.
In a forward proxy decryption scenario, the firewall generates a self-signed root CA certificate and uses it to sign per-session certificates for intercepted HTTPS traffic. If that root CA certificate is not installed in the client's trusted root certificate store, the browser will treat the per-session certificates as untrusted, resulting in certificate errors. Option C directly identifies this missing trust chain as the root cause.
Key principle: Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Answer analysis
Option-by-option breakdown
For each option: why learners choose it and why it is or isn't the right answer here.
- ✗
The firewall is using a forward trust certificate that is expired.
Why it's wrong here
An expired certificate would cause errors, but likely the certificate is self-signed and not trusted.
- ✗
The decryption policy is not applied to the correct security rule.
Why it's wrong here
Decryption is applied via decryption policy, not security rules; order might matter but not the cause of certificate error.
- ✓
The firewall's decryption root CA certificate has not been installed in the client's trusted root certificate store.
Why this is correct
Correct. Clients must trust the firewall's issuing CA to avoid certificate warnings.
Clue confirmation
The clue word "most likely" in the question point toward this answer.
Related concept
Read the scenario before looking for a memorised answer.
- ✗
The decryption policy is set to 'no-decrypt' for the traffic.
Why it's wrong here
If set to no-decrypt, traffic would pass through without decryption, so no certificate error from the firewall.
Common exam traps
Common exam trap: answer the scenario, not the keyword
The trap here is that candidates often confuse the forward trust certificate (used to sign per-session certificates) with the root CA certificate that must be trusted by clients, leading them to focus on expiration or policy placement rather than the fundamental trust chain requirement.
Detailed technical explanation
How to think about this question
Under the hood, the firewall's forward proxy decrypts SSL/TLS by acting as a man-in-the-middle: it terminates the client's TLS connection using a dynamically generated certificate signed by its own CA, then initiates a new TLS connection to the destination server. The client must trust the firewall's root CA certificate; otherwise, the browser's certificate chain validation fails because the issuer is not in the trusted root store. In real-world deployments, this root CA is typically distributed via Group Policy or MDM to avoid manual installation on every endpoint.
KKey Concepts to Remember
- Read the scenario before looking for a memorised answer.
- Find the constraint that changes the correct option.
- Eliminate answers that are true in general but not in this case.
TExam Day Tips
- Watch for words such as best, first, most likely and least administrative effort.
- Review why wrong options are wrong, not only why the correct option is correct.
Key takeaway
Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option.
Real-world example
How this comes up in practice
A practitioner preparing for the PCNSE exam encounters this exact type of scenario on the job. The correct answer here is not the most general option — it is the best answer for the specific constraint described. Answer the scenario, not the keyword: identify the specific constraint before choosing the most familiar-sounding option. Real exam questions reward reading the full scenario before eliminating options, because the constraint defines which answer fits.
What to study next
Got this wrong? Here's your next step.
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
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Core Concepts and Architecture — study guide chapter
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FAQ
Questions learners often ask
What does this PCNSE question test?
Core Concepts and Architecture — This question tests Core Concepts and Architecture — Read the scenario before looking for a memorised answer..
What is the correct answer to this question?
The correct answer is: The firewall's decryption root CA certificate has not been installed in the client's trusted root certificate store. — In a forward proxy decryption scenario, the firewall generates a self-signed root CA certificate and uses it to sign per-session certificates for intercepted HTTPS traffic. If that root CA certificate is not installed in the client's trusted root certificate store, the browser will treat the per-session certificates as untrusted, resulting in certificate errors. Option C directly identifies this missing trust chain as the root cause.
What should I do if I get this PCNSE question wrong?
Identify which exam domain this question belongs to, review the core concept, then practise similar questions from the same domain.
Are there clue words in this question I should notice?
Yes — watch for: "most likely". Probability qualifier — the question wants the most probable cause or outcome, not a guaranteed one. Eliminate low-probability options.
What is the key concept behind this question?
Read the scenario before looking for a memorised answer.
About these practice questions
Courseiva creates original exam-style practice questions with explanations and wrong-answer analysis. It does not publish real exam questions, exam dumps, or protected exam content. Learn why practice questions differ from exam dumps →
Last reviewed: Jun 25, 2026
This PCNSE practice question is part of Courseiva's free Palo Alto Networks certification practice question bank. Courseiva provides original exam-style practice questions with explanations, topic-based practice, mock exams, readiness tracking, and study analytics to help learners prepare for the PCNSE exam.
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